From the seller site:
This is a real 3 1/2 in computer Hard drive converted into a desk clock with a quartz drive movement installed. The clock measures roughly 4″w x 6″h, and runs on 1 AA battery, included. It will make a great conversation piece on your desk or a special gift for that geek you know who is so hard to shop for. Since these clocks are made from actual recycled hard drives and circuit boards, condition and model may vary slightly. Handmade in USA.
Interestingly enough, they seem to be looking for all kinds of stuff to convert into clocks, and there are options to choose the clock hands.
Only drawback: the HD doesn’t seem to be Mac OS compatible
Link: Etsy seller stuffmadefromstuff